A significant number of compounds are known to be useful in providing a cooling sensation in the mouth, in the nasal cavity and/or on skin. The best known and most widely used of these is menthol which in addition to olfaction caused a cooling response on cold receptors in the oral cavity, the nasal cavity and on skin.
Since menthol has a strong minty odor, a bitter taste and provides a burning sensation when used in high concentrations, a variety of other menthyl ester-based and menthyl carboxamide-based cooling compounds have been developed, are taught in the prior art and are used in flavor or fragrance applications. Such menthyl ester-based and menthyl carboxamide-based cooling compounds include the menthyl carboxamide, N-ethyl-p-menthane carboxamide, WS-3, trademark of the Warner Lambert Company, disclosed in U.S. Pat. No. 4,150,052, and monomenthyl succinate, monomenthyl-αα-dimethyl succinate, monomenthyl methyl succinate, monomenthyl glutarate, menthyl 2-pyrrolidone-5-carboxylate and monomenthyl 3-methyl maleate, the uses of which are disclosed in U.S. Pat. Nos. 3,111,127; 5,725,865; 5,843,466; 6,365,215 and 6,451,844.
More specifically, U.S. Pat. No. 3,111,127 discloses such monomenthyl esters as monomenthyl succinate, monomenthyl αα-dimethyl succinate and monomenthyl 2-methylmaleate covered by the generic structure: wherein R represents a menthyl radical and R′ is selected from the group consisting of ‘saturated and unsaturated aliphatic, aromatic and heteroaromatic polycarboxylic acid radicals and substituted analogues thereof and N is the total number of carboxyl groups in the acid from which the ester is derived’ for improving the flavoring characteristics when incorporated in a tobacco product. U.S. Pat. No. 4,150,052 discloses the use of N-ethyl p-menthane-3-carboxamide for its physiological cooling action on the skin, and discloses its use in, for example, chewing gum. U.S. Pat. Nos. 5,725,865 and 5,843,466 disclose the use of mono menthyl succinate for its physiological cooling action and disclose its use in, for example, carbonated beverages, alcoholic beverages and chewing gum. U.S. Pat. No. 6,365,215 discloses at Col. 11, line 3, the use of mono menthyl glutarate in oral sensory perception-affecting compositions for use with such consumable materials as chewing gums. U.S. Pat. No. 6,451,844 discloses the use of menthyl 2-pyrrolidone-5-carboxylate (QUESTICE L, Quest International, B.V. of Naarden, Netherlands) having the structure: in skin care and hair care compositions for their insect repellency properties.
Furthermore, L-mono menthyl glutarate has been registered as a GRAS flavoring substance, FEMA No. 4006 and, in Smith et al. “GRAS Flavoring Substances 20”, Food Technology, Vol. 55, No. 12, December 2001 at page 53 is indicated to have uses in nonalcoholic beverages, alcoholic beverages: chewing gum, confectionery frosting, hard candy, soft candy and snack foods.
A number of the mono menthyl half acid ester derivatives found to be useful in the practice of our invention are novel; however those that are disclosed in the prior art together with their respective syntheses, without the disclosure of utilities thereof are the compounds having the structure: where n is an integer of from 3 up to 5, as follows:                (i) L-menthyl hydrogen adipate (n=3);        (ii) L-menthyl hydrogen piel ate (n=4); and        (iii) L-menthyl hydrogen suberate (n=5)by Rule et al., “Optical Activity and the Polarity of Substituent Groups Part VIII. Growing chain Effects and the orthoEffect in Benzoic Esters”, J. Chem. Soc. 1928 (Part I), pp. 1347-136.        
In addition, a lower adjacent methylene homologue of the genus of novel compounds of our invention which genus has the structure: wherein n is an integer of from 1 to 5; wherein R is hydrogen, C1-C5 lower alkyl, 2-hydroxyethyl or cyclopropyl and wherein R′ is hydrogen, methyl or ethyl is disclosed in “SciFinder” (Nov. 20, 2002; Trademark of Chemical Abstracts Services), to wit: malonamic acid, pmentb-3-yl ester, (±)-(8CI) having CAS Registry Number 6129-88-0 where the structure is shown below: No indication of the use of the compound, malonamic acid, pmenth-3-yl ester, (±)- is set forth in the SciFinder disclosure.
Despite the existence in the prior art and in commerce of such a vast number and variety of cooling agents including mono menthyl ester-based compounds in food, cosmetic and fragrance applications, there still remains a need for cooler compounds which provide strong and substantive refreshing and cooling attributes in the absence of negative taste, negative aroma and negative cooling attributes, and more particularly there still exists a need for cooler compounds which provide good onset of effect, prolonged cooling and economy of use.